Noise characterization in a wireless communication system

ABSTRACT

The character of the noise in a series of incoming symbols received over a wireless link is determined. A series of corresponding bits are recovered based upon the series of incoming symbols. The series of corresponding bits are encoded to determine a series of recovered symbols. A vector product of the series of incoming symbols and the series of recovered symbols is determined. A difference between two symbols within the vector product is determined, wherein the two symbols were transmitted over the wireless link in close temporal proximity to one another. The expected value of a non-orthogonal noise portion of the series of incoming symbols is determined based upon an expected value of the difference between the two symbols.

CROSS REFERENCE

[0001] This application is a continuation application of co-pendingApplication Ser. No. 09/204,926, filed Dec. 3, 1998, entitled “NoiseCharacterization in a Wireless Communication System,” now allowed.

BACKGROUND OF THE INVENTION

[0002] I. Field of the Invention

[0003] The invention relates generally to wireless communications. Moreparticularly, the invention relates to signal characterization in awireless communication system.

[0004] II. Description of the Related Art

[0005] In a typical wireless communication system, a plurality of remoteunits communicate through a common base station. FIG. 1 is a blockdiagram showing a typical modem wireless communication system 10. Thesystem is comprised of a series of base stations 14. A set of remoteunits 12 communicate with the base stations 14. The remote units 12communicate with the base stations 14 over a forward link channel 18 anda reverse link channel 20. For example, FIG. 1 shows a hand-heldportable telephone, a vehicle mounted mobile telephone and a fixedlocation wireless local loop telephone. Such systems offer voice anddata services. Other modem communication systems operate over wirelesssatellite links rather than through terrestrial base stations.

[0006] In order for multiple remote units to communicate over a commonchannel, a means of multiplexing the signal onto the forward link andreverse link channels must be used. One commonly used method is codedivision multiple access (CDMA). Additional information concerning CDMAis set forth in the TIA/EIA Interim Standard entitled “MobileStation—Base Station Compatibility Standard for Dual-Mode WidebandSpread Spectrum Cellular System,” TIA/EIA/IS-95-A, and its progeny, thecontents of which are incorporated herein by reference. In a CDMAsystem, the forward and reverse link signals are modulated with aspreading code which spreads the signal energy over a band offrequencies. By correlating the incoming signal with the spreadingsequences used in the transmitting units, the signals which aretransmitted in the same frequency band at the same time can bedistinguished from one another at the receiving unit.

[0007] In general, CDMA systems operate most efficiently when eachremote unit receives the forward link signal at the minimum signalquality which is necessary in order to accurately decode the incomingsignal. If the forward link signal arrives at the remote unit at a levelthat is too low, the signal level may not be sufficient to supportreliable communications. If the forward link signal arrives at theremote unit at a level that is too high, the signal acts as unnecessaryinterference to other remote units. Therefore, the remote unit monitorsthe signal quality at which the signal is received and requests anincrease in the power level at which the base station transmits theforward link signal if the signal quality is too low and requests adecrease in the power level at which the base station transmits theforward link signal if the signal quality is above the threshold.

[0008] In order to implement such a system, in one embodiment, theremote unit estimates the forward link signal quality by determining thesignal-to-noise ratio at which it receives the forward link signal. Thesignal-to-noise ratio can be determined by finding the ratio of theenergy per bit to the non-orthogonal noise power density (E_(b)/N_(t)).The energy per bit is a measure of the energy associated with a singleinformation bit. Typically, signal-to-noise ratios are determined over aseries of bits so that an average energy per bit is determined and usedas the numerator of the signal-to-noise ratio.

[0009]FIG. 2 is a block diagram of a receiver which determines anaverage energy per bit. A decoder 30 receives a signal vector {rightarrow over (r)} corresponding to a series of N symbols which make up aframe such that {right arrow over (r)}=(r₁, r₂, . . . , r_(N)). Eachsymbol, r_(n), is comprised of a signal portion and a noise portion asshown in Equation 1 below.

r _(n) =s _(n) +w _(n)  (Eq. 1)

[0010] wherein:

[0011] r_(n) is a voltage value of the n^(th) symbol;

[0012] s_(n) is the signal portion of the n^(th) symbol in volts; and

[0013] w_(n) is the noise portion of the nth symbol in volts.

[0014] The signal component of each bit sample can be expressed in termsof a voltage level and a polarity as shown in Equation 2.

r _(n) =A _(n) d _(n) +w _(n)  (Eq. 2)

[0015] wherein:

[0016] A_(n) is the absolute value of the voltage level of the n^(th)symbol; and

[0017] d_(n) represents the polarity (i.e., digital value) of the n^(th)symbol (i.e., +/−1).

[0018] In a digital representation, the voltage level A_(n) istransmitted into a numerical value represented by digital bits.

[0019] Referring again to FIG. 2, the decoder 30 receives the symbolscorresponding to a frame represented by the vector {right arrow over(r)} and converts them to a series of bits. In one embodiment, thedecoder 30 is a Viterbi decoder. Typically, the bits output by thedecoder 30 are passed to subsequent processing stages (not shown) inorder to recreate a transmitted signal. In order to determine the energyassociated with the signal energy in the frame, the bits output by thedecoder are re-encoded by a re-encoder 32 which operates in acomplimentary manner with the decoder 30 such that the output of there-encoder 32 is the vector {right arrow over (d)}=(d₁, d₂, . . . d_(N))where d_(n) represents the polarity of the n^(th) symbol as definedabove.

[0020] The vector {right arrow over (r)} and the vector {right arrowover (d)} are input into a dot product block 34. The dot product block34 takes the dot product of the two inputs as shown in Equation 3 below.$\begin{matrix}{{\frac{1}{N}\left( {\overset{\rightarrow}{r} \cdot \overset{\rightarrow}{d}} \right)} = {\frac{1}{N}\left( {{r_{1}*d_{1}} + {r_{2}*d_{2}} + \ldots \quad + {r_{N}*d_{N}}} \right)}} & \left. {\text{(Eq}.\quad 3} \right)\end{matrix}$

[0021] The output of the square of the dot product block 34 is coupledto a squaring block 36 yielding the result given in Equation 4.$\begin{matrix}\begin{matrix}{{\frac{1}{N}\left( {\overset{\rightarrow}{r} \cdot \overset{\rightarrow}{d}} \right)} = \quad {\frac{1}{N}\left\lbrack {{\left( {{A_{1}d_{1}} + w_{1}} \right)*d_{1}} + {\left( {{A_{2}d_{2}} + w_{2}} \right)*d_{2}} +} \right.}} \\\left. {\left. \quad {\ldots \quad \left( {{A_{N}d_{N}} + w_{N}} \right)*d_{N}} \right\rbrack^{2}*d_{N}} \right\rbrack^{2}\end{matrix} & \text{(Eq.~~4)}\end{matrix}$

[0022] Note that d_(n) ²=1 for all n. We can also assume that the noisecomponent of the vector {right arrow over (r)} is a series ofindependent and identically distributed random variables with zero mean,possibly Gaussian distribution, and, thus, according to well-knownprinciples of stochastic processes, randomly multiplying the individualcomponents by +/−1 does not change the characteristics or average valueof the noise. In this way, Equation 4 reduces to Equation 5A as shownbelow. $\begin{matrix}\begin{matrix}{{\frac{1}{N}\left( {\overset{\rightarrow}{r} \cdot \overset{\rightarrow}{d}} \right)^{2}} = \left( {{\frac{1}{N}{\sum\limits_{n = 1}^{N}A_{n}}} + {\frac{1}{N}{\sum\limits_{n = 1}^{N}w_{n}}}} \right)^{2}} \\{= \left( {{\frac{1}{N}{\sum\limits_{n = 1}^{N}A_{n}}} + ɛ} \right)^{2}}\end{matrix} & \text{(Eq.~~5A)}\end{matrix}$

[0023] The second term of Equation 5A is, by definition, the mean noisecomponent of the vector {right arrow over (r)} and is equal to zero suchthat Equation 5A reduces to Equation 5B as shown below. $\begin{matrix}{{\frac{1}{N}\left( {\overset{\rightarrow}{r} \cdot \overset{\rightarrow}{d}} \right)^{2}} = {\frac{1}{N}{\sum\limits_{n = 1}^{N}A_{n}^{2}}}} & \text{(Eq.~~5B)}\end{matrix}$

[0024] Thus, the output of the square of the dot product block 34 showsthe sum of the energy of the symbols in the frame which is directlyrelated to the energy in each bit of the frame as shown in Equation 6below.

E _(b)=({right arrow over (r)}·{right arrow over (d)})² /B  (Eq. 6)

[0025] wherein: B is the number of bits in a frame.

[0026] In order to determine the signal-to-noise ratio, an estimate ofthe noise component of the signal must also be determined. In general,we are only interested in the non-orthogonal portion of the noise,N_(t), because any orthogonal portion of the noise can be removed bysignal processing. Non-orthogonal noise sources include thermal noise,forward link transmissions from neighboring base stations and multipathpropagations from the servicing base station. Estimation of thenon-orthogonal component of the noise is more difficult than theestimation of the bit energy in general. Although several techniqueshave been discussed, they tend to be inaccurate or require an excessiveamount of processing resources. For example, one means of determiningthe non-orthogonal noise energy is disclosed in U.S. Pat. No. 5,754,533entitled “METHOD AND SYSTEM FOR NON-ORTHOGONAL NOISE ENERGY BASED GAINCONTROL.” According to one embodiment of the patent, a pilot channel orother known channel is demodulated and used to determine thenon-orthogonal noise level. In such a case, a separate demodulationprocess is carried out for each multipath component of the signal. Basedon the result of the demodulations, a noise component is separatelymeasured for each multipath. The use of a pilot signal increases thecosts of the system and decreases the capacity of the system. Thedemodulation of each separate multipath occurrence and the individualcalculations consume significant system resources.

[0027] Therefore, there has been a long-felt need in the industry for anefficient determination of non-orthogonal noise characteristics in adigital communication system.

SUMMARY OF THE INVENTION

[0028] In order to estimate the orthogonal noise level in a wirelesscommunication system, a series of incoming symbols received over awireless link are decoded to produce a series of corresponding bits. Theseries of corresponding bits are encoded to produce a series ofrecovered symbols. A vector product of the series of incoming symbolsand the series of recovered symbols is determined. A difference betweentwo symbols within the vector product which were transmitted over thewireless link in close temporal proximity to one another is determined.The expected value of the difference between the two symbols isdetermined. The expected value of a non-orthogonal noise portion of theseries of incoming symbols is determined based upon the expected valueof the differences. In one embodiment, a signal quality of the series ofincoming symbols is determined based upon the expected value of thenon-orthogonal noise portion.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The features, objects and advantages of the present inventionwill become more apparent from the detailed description set forth belowwhen taken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout and wherein:

[0030]FIG. 1 is a block diagram showing a typical modern wirelesscommunication system.

[0031]FIG. 2 is a block diagram of a receiver which determines anaverage energy per bit.

[0032]FIG. 3 is a block diagram showing one embodiment of thenon-orthogonal noise determination process of the invention.

[0033]FIG. 4 is a flowchart showing operation of the noise estimationprocess in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0034] Providing an efficient and effective means for determining thesignal quality of a received signal is an important factor in designinga CDMA wireless system which effectively uses the available capacity.While several effective methods have been developed to measure thesignal energy which consumes a reasonable amount of processingresources, to date, the means and methods available for measuring thenon-orthogonal noise component have been fairly complex. For example,previously developed schemes involve the estimation of thenon-orthogonal noise component based upon demodulation of the pilotsignal. Such schemes rely on a set of steps which are performed for eachindividual multipath propagation of the pilot signal received at theremote unit. Although such a process is effective, it is desirable tofind a way to determine the non-orthogonal noise component of a receivedsignal based upon the combined signal rather than the individualmultipath components. The invention described herein operates on thecombined signal and can be practically implemented without consuming anexcessive amount of resources.

[0035]FIG. 3 is a block diagram showing one embodiment of thenon-orthogonal noise determination process. Some of the components (suchas a de-interleaver 50, a rate decision block 54 and an interleaver 58)shown in FIG. 3 are dependent upon the processes implemented by thetransmitter. These elements are included in the FIG. 3 for the purposeof illustration but may not be necessary in systems which do notincorporate interleaving or multiple data rate transmission. In oneembodiment, the components shown in FIG. 3 are incorporated in a remoteunit which operates in a cellular environment.

[0036] Interleaving is the process by which the symbols output by aViterbi encoder within a transmitter are re-ordered before transmission.Because of the redundancy introduced by Viterbi encoding, at the outputof a Viterbi encoder, successive symbols contain redundant information.Typically, errors introduced during the transmission process operate ona series of consecutive symbols. The Viterbi decoding process canrecreate a perfect bit stream from an imperfect symbol stream, if atleast a portion of the symbol energy corresponding to any one bit issuccessfully transmitted. Therefore, in order to reduce the probabilitythat all of the symbols corresponding to a given bit will be corruptedduring the transmission process, the symbols are arranged in anon-consecutive order before transmission. At the receiver, the symbolsare re-ordered before they are decoded.

[0037] The de-interleaver 50 arranges the symbols in the order in whichthey were produced by the Viterbi encoder at the transmitter. There-ordered symbols output by the de-interleaver 50 are input into aViterbi decoder 52. The Viterbi decoder 52 produces a bit streamaccording to well-known Viterbi decoding techniques. In one embodiment,the transmitter is capable of sending data at more than one data rate.In order to fully decode the data, a decision must be made as to therate at which the data was sent. The bit stream output by the Viterbidecoder 52 is input into the rate decision block 54. The rate decisionblock 54 may operate in accordance with, for example, U.S. Pat. Nos.5,566,206 and 5,774,496 each entitled “METHOD AND APPARATUS FORDETERMINING DATA RATE OF TRANSMITTED VARIABLE RATE DATA IN ACOMMUNICATIONS RECEIVER,” assigned to the assignee hereof andincorporated herein by this reference in their entirety. The data ratedecision block 54 outputs a series of bits at the rate at which theywere transmitted and also, in one embodiment, outputs an indication ofthat rate. The output of the rate decision block 54 is subjected tofurther signal processing (not shown). In addition, the output of therate decision block 54 is passed to a re-encoder 56.

[0038] The re-encoder 56 encodes the data in the same manner as thetransmitter, thus converting the series of recovered data bits to aseries of recovered symbols. The recovered symbols are output from there-encoder 56 and input into the interleaver 58. The interleaver 58operates in the same manner as the interleaver in the transmitter andre-orders the recovered symbols in a non-consecutive order correspondingto the order as the incoming symbols were transmitted over the air.

[0039] A vector product block 60 multiplies the received vector with therecovered vector. A difference block 62 determines a difference betweensets of two values which correspond to two symbols which weretransferred in close temporal proximity to one another over the wirelesslink. A noise estimation block 64 determines the statisticalcharacteristics of noise based upon the statistical characteristics ofthe output of the difference block 62. In one embodiment, the noiseestimation block 64 determines the expected value of the non-orthogonalnoise component of the incoming signal. In another embodiment, theoutput of the noise estimation block 64 is coupled to a signal qualitydetermination unit which determines the signal-to-noise ratio at whichthe signal is received. In yet another embodiment, the output of thenoise estimation block 64 is coupled to a power control block whichrequests an increase or decrease in transmission power based upon thestatistical characteristics of noise.

[0040] The blocks shown in FIG. 3 can be embodied in a plurality ofmedia using a variety of well-known techniques. For example, the blocksin FIG. 3 can be embodied in field programmable gate arrays (FPGA),application specific integrated circuits (ASIC), software running on amicroprocessor as well as other media.

[0041] The operation of the invention may be understood by reference tothe following explanation and equations. The received symbols can beexpressed in terms of the vector {right arrow over (r)} and theindividual symbol components of the vector r can be expressed as shownbelow in Equation 7.

{right arrow over (r)}=[r ₁ , r ₂ , . . . r _(N)]=[(A ₁ d ₁ +w ₁), (A ₂d ₂ +w ₂), . . . (A _(N) d _(N) +w _(N))]  (Eq. 7)

[0042] wherein:

[0043] r_(n) is a voltage value of the nth symbol;

[0044] w_(n) is the noise portion of the nth symbol in volts;

[0045] A_(n) is the absolute value of the voltage level of the signalportion of the nth symbol; and

[0046] d_(n) represents the polarity (i.e., digital value) of the n^(th)symbol (i.e., +/−1).

[0047] The process of decoding, re-encoding and re-interleaving thereceived vector {right arrow over (r)} produces a recovered vector{right arrow over (d)} which represents symbol values in the order inwhich they were transmitted, e.g. the order in which they were receivedin the vector {right arrow over (r)} as shown in Equation 8.

{right arrow over (d)}=[d ₁ , d ₂ . . . d _(N)]  (Eq. 8)

[0048] wherein:

[0049] d_(n)=polarity of the n^(th) symbol value, (i.e., +/−1).

[0050] By taking the vector product of the received vector {right arrowover (r)} and the recovered vector {right arrow over (d)}, Equation 9 isgenerated. $\begin{matrix}\begin{matrix}{\left( {\overset{\rightarrow}{r}*\overset{\rightarrow}{d}} \right) = \quad \left\lbrack {\left( {{A_{1}*d_{1}*d_{1}} + {w_{1}*d_{1}}} \right),\left( {{A_{2}*d_{2}*d_{2}} + {w_{2}*d_{2}}} \right),} \right.} \\\left. \quad {\ldots \quad,\left( {{A_{N}*d_{N}*d_{N}} + {w_{N}*d_{N}}} \right)} \right\rbrack \\{= \quad \left\lbrack {\left( {{A_{1}*d_{1}^{2}} + {w_{1}*d_{1}}} \right),\left( {{A_{2}*d_{2}^{2}} + {w_{2}*d_{2}}} \right),\ldots \quad,} \right.} \\\left. \quad \left( {{A_{N}*d_{N}^{2}} + {w_{N}*d_{N}}} \right) \right\rbrack \\{= \quad \left\lbrack {\left( {A_{1} + {w_{1}*d_{1}}} \right),\left( {A_{2} + {w_{2}*d_{2}}} \right),\ldots \quad,} \right.} \\\left. \quad \left( {A_{N} + {w_{N}*d_{N}}} \right) \right\rbrack \\{= \quad {\left\lbrack {p_{1},p_{2},\ldots \quad,p_{N}} \right\rbrack = \overset{\rightarrow}{p}}}\end{matrix} & \left( {{Eq}.\quad 9} \right)\end{matrix}$

[0051] Because d_(n) ² is equal to one for all values of n, the equationreduces as shown above.

[0052] In order to extract the noise component, the difference betweentwo consecutive symbol values is taken as shown below in Equation 10.$\begin{matrix}\begin{matrix}{X_{1,2} = \left( {p_{1} - p_{2}} \right)} \\{= {A_{1} - A_{2} + \left( {{w_{1}*d_{1}} - {w_{2}*d_{2}}} \right)}}\end{matrix} & \text{(Eq.~~10)}\end{matrix}$

[0053] Note that if A₁ is equal to A₂, these values cancel one anotherand the component which is left is given in Equation 11. $\begin{matrix}\begin{matrix}{X_{1,2} = {{w_{1}d_{1}} - {w_{2}d_{2}}}} \\{= {w_{1} - w_{2}}}\end{matrix} & \text{(Eq. 11)}\end{matrix}$

[0054] The noise component of the vector {right arrow over (r)} is aseries of independent and identically distributed random variables withzero mean, possibly Gaussian distribution, and, thus, according towell-known principles of stochastic processes, randomly multiplying theindividual components by +/−1 does not change the characteristics oraverage value of the noise. Therefore, as shown in Equation 11, thepolarity of the symbols, d_(n), can be removed without a loss ofinformation concerning the characteristics of the non-orthogonal noise.

[0055] As is well-known in the art of probability, random variables, andstochastic processes, the expected value of a Gaussian random variablecan be estimated by finding the expected value of the difference betweenthe two values of the random variable as shown in Equation 12.

E{(w _(i) −w _(j))²}=2σ² =N _(t)  (Eq. 12)

[0056] However, it should be noted that other estimators exist. Forexample, if the statistics of the noise are Gaussian, an unbiasedestimate of N_(t) can be obtained by taking the absolute value of thedifference between two values of the random variable and multiplying ittimes a known scaling factor as shown in Equation 13.

E{|w _(i) −w _(j) |}=N _(t) *K  (Eq. 13)

[0057] wherein: K is equal to a known scaling factor.

[0058] Use of Equation 13 may be advantageous in some implementationsbecause it avoids a squaring operation which is required by Equation 12,thus, perhaps resulting in faster execution and more efficient use ofprocessing resources. Applying these principles, the noise power can beestimated by summing the squares of the difference over the entire frameas shown in Equation 14.

N _(t)(X _(1,2) ² +X _(3,4) ² + . . . +X _(N-1,N) ²)*S  (Eq. 14)

[0059] wherein: S is a scaling factor.

[0060] As noted above, the invention operates on the assumption that thevoltage level corresponding to two consecutive symbols are approximatelythe same. For example, A₁ is equal A₂, A₃ is equal to A₄ and so on. Ifthe symbols are interleaved over a frame for transmission, thedifference should be taken between two symbols that were transmitted inclose temporal proximity to one another over the channel, such asconsecutively or simultaneously. Fortunately, the assumption that thevoltage levels of successive signals are equal is valid in manycommunication systems. For example, if binary phase shift keying (BPSK)modulation is used such as in IS-95-A rate set 1 and rate set 2operation, the two consecutive symbols are transmitted in sequence atthe same power level. Because the symbol duration is typically verysmall such as on the order of 50 microseconds, the two voltages arenearly equal as the channel does not typically change substantially in50 microseconds. If quadrature phase shift keying (QPSK) modulation isused, the two symbols can be selected which have been transmitted at thesame power level at the same time over the channel. For example, r₁ istransmitted on the in-phase channel and r₂ is transmitted on thequadrature channel at the same time and, thus, the voltages aretheoretically identical.

[0061]FIG. 4 is a flowchart showing the noise characterization processin accordance with the invention. In block 70, a series of incomingsymbols are received and stored. In block 72, the corresponding bits arerecovered and re-encoded to produce a series of digital bit values. Asshown above, in one embodiment, this process involves de-interleavingand re-interleaving the symbols. Also as shown above, in anotherembodiment, this process involves determination of a transmission rate.In block 74, the vector product of the received symbols and therecovered symbols is taken. In block 76, the difference betweencorresponding consecutive symbols is taken. In block 78, the expectedvalue of the difference between the consecutive symbols is taken whichis directly related to the expected value of the noise component of thestored series of incoming symbols. In block 80, the expected value ofthe noise is used to determine the signal quality (i.e., Eb/Nt) of theforward link signal. Based upon the signal quality, block 82 requests anincrease or decrease in power of the signal. In an alternativeembodiment, the block 82 may request an increase or decrease in datarate in a similar manner.

[0062] Upon examination of the above written description, a myriad ofalternative embodiments within the scope of the invention will bereadily apparent to one skilled in the art. For example, in one aspectof the invention, consecutive symbols as transmitted or simultaneoussignals as transmitted are subtracted from one another. In theembodiment shown above, this is accomplished by re-ordering the coveredsymbols and taking the vector product of the received symbols and therecovered symbols. Obviously, in other embodiments, these processes canbe accomplished without the actual re-ordering of the recovered symbols.Instead, a mapping algorithm can be used to associate consecutively orsimultaneously transmitted symbols without re-ordering. In addition, theinvention was described with reference to a Viterbi encoder and Viterbidecoder combination. Other types of encoders and decoders can be used inconjunction with the teachings of the invention. In the descriptionabove, a determination of the characteristics of the non-orthogonalportion of the noise is used to determine a signal-to-noise ratio of aforward link signal which is in turn used to request an increase ordecrease in forward link transmission power from the base station. Inother embodiments, the characteristics of the noise are determined foranother purpose such as load determination or access control. In someembodiments, the invention can be used to determine higher ordercharacteristics of the non-orthogonal component of the noise. Forexample, a higher order moment of the noise can be determined. Theinvention can be applied on either the forward link or the reverse linkand, thus, can be housed at either the base station or the remote unitor other type of unit. The invention can be embodied in terrestrial andsatellite systems as well as other types of systems.

[0063] The invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiment is to be considered in all respects only as illustrative andnot restrictive and the scope of the invention is, therefore, indicatedby the appended claims rather than the foregoing description. Allchanges which come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

What is claimed is:
 1. A method of noise estimation, comprising the steps of: storing a series of incoming symbols received over a wireless link; decoding said series of incoming symbols to produce a series of corresponding bits; encoding said series of corresponding bits to produce a series of recovered symbols; determining a vector product of said series of incoming symbols and said series of recovered symbols; determining a difference between two symbols within said vector product, wherein said two symbols were transmitted over said wireless link in close temporal proximity to one another; and determining an expected value of said difference between said two symbols so as to define an expected value of a non-orthogonal noise portion of said series of incoming symbols.
 2. The method of claim 1 , further comprising the step of arranging said series of recovered symbols in an order corresponding to the order in which said series of incoming symbols were transmitted over said wireless link.
 3. The method of claim 1 , further comprising the step of determining a data rate at which said series of incoming symbols were transmitted over said wireless link.
 4. The method of claim 1 , further comprising the step of determining a signal quality of said series of incoming symbols based upon said expected value of said non-orthogonal noise portion.
 5. The method of claim 1 , further comprising the step of requesting an increase or decrease in transmission power based upon said expected value of said non-orthogonal noise portion.
 6. A receiver, comprising: means for storing a series of incoming symbols received over a wireless link; means for decoding said series of incoming symbols to produce a series of corresponding bits; means for encoding said series of corresponding bits to determine a series of recovered symbols; means for determining a vector product of said series of incoming symbols and said series of recovered symbols; means for determining a difference between two symbols within said vector product, wherein said two symbols were transmitted over said wireless link in close temporal proximity to one another; and means for determining an expected value of said difference between said two symbols so as to define an expected value of a non-orthogonal noise portion of said series of incoming symbols.
 7. The receiver of claim 6 , further comprising means for arranging said series of recovered symbols in an order corresponding to the order in which said series of incoming symbols were transmitted over said wireless link.
 8. The receiver of claim 1 , further comprising means for determining a data rate at which said series of incoming symbols were transmitted over said wireless link.
 9. The receiver of claim 1 , further comprising means for determining a signal quality of said series of incoming symbols based upon said expected value of said non-orthogonal noise portion.
 10. The receiver of claim 1 , further comprising means for requesting an increase or decrease in transmission power based upon said expected value of said non-orthogonal noise portion.
 11. A receiver comprising: a decoder having an input port configured to receive a series of incoming symbols over a wireless link and having an output port configured to produce a series of recovered data bits; an encoder having an input port coupled to said output port of said decoder and having an output port configured to produce a series of encoded symbols; a vector product block having a first input port coupled to said output port of said encoder and having a second input port configured to receive said series of incoming symbols and having an output port configured to produce a vector product of said series of encoded symbols and said series of incoming symbols; a difference block having an input port coupled to said output port of said vector product block and having an output port configured to produce differences between sets of two values of said vector product, wherein said sets of two values correspond to two symbols which were transferred over said wireless link in close temporal proximity to one another; and a noise estimation block having an input port coupled to said output port of said difference block and configured to determine a statistical characteristic of said differences.
 12. The receiver of claim 11 , further comprising a interleaver coupled between said encoder and said vector product block, said interleaver configured to arrange said series of recovered symbols are in an order corresponding to the order in which said series of incoming symbols were transmitted over said wireless link.
 13. The receiver of claim 11 , further comprising a rate decision block coupled between said decoder and said encoder, said rate decision block configured to determine a rate at which said series of incoming symbols were transmitted over said wireless link.
 14. The receiver of claim 11 , further comprising a signal quality determination unit configured to determine a signal quality of said series of incoming symbols based upon said statistical characteristic of said differences.
 15. The receiver of claim 1 , further comprising a power control block coupled to said noise estimation block, said power control block configured to request an increase or decrease in transmission power based upon said statistical characteristic of said difference. 